An explicit-implicit method for flexible-rigid multibody systems

The solution of problems which include both flexible and rigid bodies is ad dressed in this paper. An explicit time integration scheme along with a fin ite element semidiscretization procedure is employed for the flexible bodie s, whereas an implicit conserving scheme is adopted for the rigid bodies. F or elements in each flexible body which lie on an interface with a rigid bo dy, a node-based partitioning scheme is introduced. In each half-time step where the balance of momentum is enforced, the explicit nodes are integrate d first. The results are used subsequently as boundary conditions for the i ntegration of the implicit nodes. The implicit nodes which lie on an interf ace of a rigid body are constrained to follow the motion of the rigid body by a Lagrange multiplier method. This leads to a modification of the inerti al properties of the attached rigid body, and results in an iterative solut ion procedure involving six parameters: three for translations and three fo r rotations. The overall algorithm is shown to be momentum conserving. Mode l problems are presented for examining the applicability and the conserving property of the scheme. (C) 2001 Published by Elsevier Science B.V.